Articles by Jurģis Jansons

The overall increase of ungulate populations in modern Europe has contributed to conflicts in national economies, particularly between game management and the forestry sector. This study assessed damage risks to young pine (Pinus sylvestris L.), spruce (Picea abies (L.) H. Karst.) and aspen (Populus tremula L.) stands at two spatial scales. One level assessed the interaction between sex-age structure of cervid populations, measured by pellet group density, and forest damages, measured as the percentage of heavily browsed trees in 2040 stand surveys distributed proportionally throughout the country. The second level compared pellet counts and trail-camera-based records of moose (Alces alces L.) and red deer (Cervus elaphus L.) presence in a pilot study area. We examined whether 1) there is a correlation between damage amount and ungulate population structure and 2) are the data from trail cameras suitable for wider use in monitoring ungulate population structure. The study confirmed significantly higher moose pellet group densities in pine than in spruce and aspen stands. Pine damages were greater in stands with higher moose pellet group density, especially with female moose prevailing over male moose density index. The red deer pellet group densities were significantly higher in heavily damaged pine and spruce stands, regardless of sex-age structure. In most cases, there were no statistically significant differences between the two survey methods of ungulate population structure by using pellet count transects and trail camera fixations. Both methods provide comparable data on sex-age structure in moose and red deer populations if seasonal and habitat-predicted biases are considered. However, trail cameras are more widely applicable and easier to use by hunters than pellet counts.

• Done, Latvian State Forest Research Institute ‘Silava’, Riga street 111, Salaspils, LV-2169, Latvia https://orcid.org/0000-0002-2122-7154 E-mail: gundega.done@silava.lv
• Ozoliņš, Latvian State Forest Research Institute ‘Silava’, Riga street 111, Salaspils, LV-2169, Latvia https://orcid.org/0000-0002-6647-9128 E-mail: janis.ozolins@silava.lv
• Bagrade, Latvian State Forest Research Institute ‘Silava’, Riga street 111, Salaspils, LV-2169, Latvia https://orcid.org/0000-0002-1031-0665 E-mail: guna.bagrade@gmail.com
• Jansons, Latvian State Forest Research Institute ‘Silava’, Riga street 111, Salaspils, LV-2169, Latvia E-mail: jurgis.jansons@silava.lv
• Baumanis, Latvian State Forest Research Institute ‘Silava’, Riga street 111, Salaspils, LV-2169, Latvia E-mail: jbaumanis@inbox.lv
• Vecvanags, Institute for Environmental Solutions ‘Lidlauks’, Cēsis, LV-4126, Latvia https://orcid.org/0000-0003-1233-764X E-mail: alekss.vecvanags@vri.lv
• Jakovels, Institute for Environmental Solutions ‘Lidlauks’, Cēsis, LV-4126, Latvia https://orcid.org/0000-0002-2969-5972 E-mail: dainis.jakovels@vri.lv

The aim was to investigate relative susceptibility of stumps of spruce and pine to airborne infections by Heterobasidion following pre-commercial thinnings. The proportions of infected stumps and colonized stump surface areas were analysed in 16 forest stands. In total, 746 spruce and 1063 pine stumps were sampled, and 184 and 105 infected stumps, respectively, were analysed. In conclusion, the present study demonstrated that in the investigated area: i) both Heterobasidion infection frequency and the extent of surface colonization correlated positively with stump diameter of both spruce and pine; ii) spruce stumps were significantly more often subjected to primary infections than pine stumps; iii) the pathogen exhibited more extensive surface colonization of spruce stumps than of pine stumps.

• Gaitnieks, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia E-mail: talis.gaitnieks@silava.lv
• Brauners, JSC “Latvia’s State Forests”, 1 Vainodes str., Riga, LV-1004, Latvia E-mail: i.brauners@lvm.lv
• Kenigsvalde, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia E-mail: kristine.kenigsvalde@silava.lv
• Zaļuma, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia E-mail: astra.zaluma@silava.lv
• Brūna, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia E-mail: lauma.bruna@silava.lv
• Jansons, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia E-mail: jurgis.jansons@silava.lv
• Burņeviča, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia E-mail: natalija.arhipova@silava.lv
• Lazdiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia E-mail: andis.lazdins@silava.lv
• Vasaitis, Swedish University of Agricultural Sciences (SLU), P.O. Box 7026, SE-75007 Uppsala, Sweden E-mail: Rimvys.Vasaitis@slu.se

The objective of this study was to investigate basic density and its within-stem variation by studying 84 European aspen stems from 28 forest stands in Latvia. The studied forest stands covered all age classes from young stands to matured forests in representative growth conditions of European aspen. The densities of 2722 wood and 1022 bark specimens were measured from the sampled trees. Only the knot-free wood specimens without obvious wood defects were chosen for analyses. A map of basic density summarizing its radial and axial variations was constructed to show species-specific, within-stem variability and the relationships between density and tree and stand variables were examined. Stem wood and bark of the European aspen show different patterns of basic density variation along the tree stem. Wood density increases from pith to bark up to certain dimensions and shows a slight decrease afterwards. The weighted basic density of bark (446 ± 39.6 kg m^–3) was higher than stem wood density (393 ± 30.4 kg m^–3). Our results suggest that wood and bark density measurements obtained at breast height can be used for reliable estimation of the densities of whole-tree stem components, while tree parameters such as diameter at breast height (DBH), tree height and social status or stand parameters, including number of trees, basal area and age, are weak predictors in this context.

• Liepiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: janis.liepins@silava.lv
• Ivanovs, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: janis.ivanovs@silava.lv
• Lazdiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: andis.lazdins@silava.lv
• Jansons, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: jurgis.jansons@silava.lv
• Liepiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: kaspars.liepins@silava.lv